Dark-adapted retinal function can be best characterized using an amplitude versus intensity pl t of the data. Further non-linear analysis of these data show, however, that an entire array of complex data can be reduced to 3 simple yet very telling numbers. One number, the slope of the sigmoid-shaped response curve, was shown to correlate highly with both positive symptoms and abnormal involuntary movements in chronic schizophrenic subjects, another link between retinal function and psychiatric disturbance. An additional study showed just how many data points along the response curve were required to generate meaningful data and is referred to as sampling adequacy in non-linear analysis. Since curve fitting of dark-adapted electroretinogram (ERG) data proved to be such a powerful technique, we have also begun to characterize a method for curve fitting of light-adapted data. In the first leg of this study, we determined at what levels of background illumination a subject was adequately light-adapted under ganzfeld conditions.